I used the bag method with water and placed it on the starboard side of the starboard engine near the harmonic balancer. That seem to work really really well. I never received three dashes. It worked flawlessly the whole day. Then that night I prep the area and taped it down with some petroleum jelly and took it out the next day to make sure before I glued it down. That didn't seem to work as well and I got plenty of three dashes during the day. I fiddled around with that location and added some more petroleum jelly. It seem to do a lot better but not as well as it did in the bag with water method. Maybe it would do a lot better being glued down. But I hate to find that out the hard way.
So now I'm questioning whether that's a best spot.
Yes, back by the bilge in the center of the boat looks like a great place. But getting myself back there to work is the hard part.
One other thing. For power I tapped into the gas gauge and that worked really great. Because now with the boat off anytime I want to check the depth I just hit one of the engine start buttons. I get a reading and it automatically shuts off after 30 seconds.
Thanks.